1. Field
The present invention relates to a light emitting diode assembly and a method for fabricating the same.
2. Discussion of the Background
A light emitting diode (LED) is basically a PN junction diode that comprises a junction of a P-type semiconductor and an N-type semiconductor.
In an LED, after a P-type semiconductor and an N-type semiconductor are joined together, current is allowed to flow into the LED by applying power to the P-type and N-type semiconductors. Then, holes in the P-type semiconductor move toward the N-type semiconductor while electrons in the N-type semiconductor move toward the P-type semiconductor, so that the electrons and holes move to the PN junction portion.
While falling from a conduction band to a valance band, the electrons moving to the PN junction portion are combined with the holes. Here, energy radiates to an extent corresponding to the difference between the heights of the conduction and valance bands, i.e., the energy difference between the energies of the conduction and valance bands. Here, the energy is emitted in the form of light.
Such LEDs are semiconductor devices that emit light, and have characteristics of environment friendliness, low voltage, long lifespan, low price, and the like. Conventionally, the LEDs were frequently applied to lamps for display or devices for displaying simple information such as numerals. However, with the development of industrial technologies, particularly with the development of information display and semiconductor technologies, the LEDs have recently been used in various applications such as displays, illuminating devices, headlights for automobile, and projectors.
Meanwhile, an LED may be formed as an LED chip by growing or depositing an N-type semiconductor and a P-type semiconductor on a growth substrate or the like. Further, an LED assembly may be formed by mounting the LED chip on a carrier substrate such as a submount.
Here, there are several methods for mounting the LED chip on the carrier substrate or the like.
In a first mounting method, an LED chip is aligned on a carrier substrate and then mounted on it through wire bonding.
In a second mounting method, a bump is formed on an LED chip, and the LED chip is directly mounted on a carrier substrate or the like through flip bonding by using the bump.
Here, the second method for directly mounting the LED chip by using the bump is one of methods for mounting a flip chip.
Among LED chips, an ultraviolet LED chip that emits light having a wavelength of an ultraviolet region is frequently mounted in the form of a flip chip because of light absorption by a P-type semiconductor layer and heat generation caused by the light absorption.
Meanwhile, the second mounting method can achieve miniaturization, lightweight, cost reduction and the like, as compared with the first mounting method using the wire bonding. However, it is required to improve reliability such as the lifespan of an LED assembly.